How compare the different between two pictures using matlab?

Hi,
I have found the way to deal with images list using list. I define imageList {'image1', 'image2', 'image3', ...., 'image10'} as a list of all images. After that I use a for loop running from 1 to the length of list, use the second for loop inside the first one, if the index in the second is different the index in the first loop, it will print out the list of file. The problem now I have is how to call the function findsim(im1,im2) in file findsim.m in this context. I use
findsim(imageList{index1}, imageList{index2}) but it didn't display anything.
Function findsim(im1,im2) now below:
Can anyone take a look at it and suggest me?

function histErr = findsim(im1,im2)
 
Im1 = imread(im1);
Im2 = imread(im2);
 
Im1 = im2double(Im1);
Im2 = im2double(Im2);
 
hn1 = imhist(Im1)./numel(Im1);
hn2 = imhist(Im2)./numel(Im2);
 
histErr = sum((hn1 - hn2).^2);

                                              

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I only have problem with below code:

disp(['----', imageList{index2}, ': ', 'Error = ', findsim(imageList{index1}, imageList{index2})]);

The result will be:

Image name from  imageList. Error=
Image name from  imageList. Error=
Image name from  imageList. Error=
Image name from  imageList. Error=
.....

If I move the findsim function to below, it works.
disp(['----', imageList{index2}, ': ', 'Error = ']);
findsim(imageList{index1}, imageList{index2});


The result will be:
Image name from  imageList. Error=
Ans = results 1
Image name from  imageList. Error=
Ans = results 2
Image name from  imageList. Error=
Ans = results 3
Image name from  imageList. Error=
Ans = results 4
.....

How to make it in the same line and arrange it in the order from minimum to maximum?

imageList = {'image1.png', 'image2.png','image3.png','image4.png', 'image5.png',
'image6.png','image7.png','image8.png','image9.png','image10.png'}
 
for i=1ndex1:length(imageList)
	    for index2 = 1:length(imageList) 
        if (index 2 ~= index1)
            disp(['----', imageList{index2}, ': ', 'Error = ', findsim(imageList{index1}, imageList{index2})]);
        end
    end
    
end

                                              

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To add the function result to your output string convert it to string first with num2str:
[ ... num2str(findsim(...))];
Use second argument if you want to control precision.
Or you can use fprintf function (see below).

To arrange from min to max you have to calculate all the distances first, sort them, and only then display.
Check the code below. I didn't test it thoroughly but it should work. Let me know in case of problems.

imageList = {'image1.png', 'image2.png','image3.png','image4.png',...
    'image5.png','image6.png','image7.png','image8.png',...
    'image9.png','image10.png'};
imNum = length(imageList);
imdist = zeros((imNum^2-imNum)/2,3);
count=0;
for index1 = 1:imNum
    for index2 = index1+1:imNum
        count = count + 1;
        imdist(count,:) = [image1 image2 findsim(imageList{index1},...
            imageList{index2})];
    end
end
[imdistsorted, idx] = sort(imdist(:,3));
% display the marix
disp(imdist(idx,:))
% display formatted
for i = idx
    fprintf('Error between %s and %s is %d\n',...
        imageList{imdist(i,1)},imageList{imdist(i,2)},imdist(i,3));
end
                                              

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You may consider reading the images outside of the function. Because your code will actually read the same images several times. You can read all the images at once to a cell array, then distance calculations will be faster, but will it take more memory. Depending on amount and size of your images think what is more important for you - memory or speed.

Thank you yuk99.

I have the function findsim in file findsim.m, now I want to use it here. I have changed a little to make it works. As in your code:

imdist(count,:) = [image1 image2 findsim(imageList{index1}, imageList{index2})];

I see error:
??? Undefined function or variable 'image1'

AFAIK, image1 and image2 here is imageList{index1} and imageList{index2}. So I change it. And I received this error:

??? Subscripted assignment dimension mismatch.

Error in ==> tmp at 20
       imdist(count,:) = [imageList{index1} imageList{index2}
       findsim(imageList{index1},imageList{index2})];

Could you please tell me why ?

I also don't clearly understand these lines of code:
imdist = zeros((imNum^2-imNum)/2,3);
Why you use (imNum^2-imNum)/2 here?

As the for loop, I think it only display the error between each image in the whole. But what I want is get one image as a template and findsim of this one to all remain image, and sort it. I'm not sure this code above can do it.

Thank you yuk99.

I have the function findsim in file findsim.m, now I want to use it here. I have changed a little to make it works. As in your code:

imdist(count,:) = [image1 image2 findsim(imageList{index1}, imageList{index2})];

I see error:
??? Undefined function or variable 'image1'

AFAIK, image1 and image2 here is imageList{index1} and imageList{index2}. So I change it. And I received this error:

??? Subscripted assignment dimension mismatch.

Error in ==> tmp at 20
       imdist(count,:) = [imageList{index1} imageList{index2}
       findsim(imageList{index1},imageList{index2})];

Could you please tell me why ?

I also don't clearly understand these lines of code:
imdist = zeros((imNum^2-imNum)/2,3);
Why you use (imNum^2-imNum)/2 here?

As the for loop, I think it only display the error between each image in the whole. But what I want is get one image as a template and findsim of this one to all remain image, and sort it. I'm not sure this code above can do it.

imageList = {'image1.png', 'image2.png','image3.png','image4.png','image5.png','image6.png','image7.png','image8.png','image9.png','image10.png'};
 
imNum = length(imageList);
imdist = zeros((imNum^2-imNum)/2,3);
count = 0;
for index1 = 1:imNum
    for index2 = index1+1:imNum
        count = count + 1;
        imdist(count,:) = [imageList{index1} imageList{index2} findsim(imageList{index1},imageList{index2})];
    end
end
 
[imdistsorted, idx] = sort(imdist(:,3));
% display the marix
disp(imdist(idx,:))
% display formatted
for i = idx
    fprintf('Error between %s and %s is %d\n', imageList{imdist(i,1)},imageList{imdist(i,2)},imdist(i,3));
end

                                              

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For the first error, sorry, it should be index1 and index2.

imdist = zeros((imNum^2-imNum)/2,3); do memory pre-allocation. Number of rows calculated as number of unique combinations (distance between images 1 and 2 is the same as between 2 and 1). 3 is number of columns to hold image indexes and the distance. Of course, this matrix is for doubles only, you cannot put strings there. If you want image names together with distance in one matrix use cell array.

Of course, you can do it for one image and compare it with the rest of images. Just assign a constant to index1.

imdist = zeros(imNum-1,3);
 
index1 = 1 % or 2 etc
for index2 = 1:imNum
    if (index 2 ~= index1)
        count = count + 1;
        imdist(count,:) = [imageList{index1} imageList{index2} findsim(imageList{index1},imageList{index2})];
    end
end
                                              

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What i mean is using one image as a template and compare with the remain 9 pictures.
Pic 1 compare to pic 2->pic10
Pic 2 compare to pic 1 and pic 3->pic10
.............
Pic 8 compare to pic1-> pic 7 and pic9->pic10
Pic 9 compare to pic1-> pic 8 and pic 10
Pic 10 compare to pic1->pic 9

So I think I need 10 matrix to arrange, right? So I have to use a big for loop for index1 to get it run as the above code?

I will try it and will comeback if I can't. Thank you very much!